About statistical process control

Statistical process control (SPC) is a method for achieving quality control in processes. It is a set of methods using statistical tools such as mean, variance and others, to detect whether the process observed is under control.

Cusum methods

The BS 5703 series of standards explain ‘cusum’, or ‘cumulative sum’, a pictorial method of interpreting data arranged in any meaningful sequence.

The data can range from overall business figures such as turnover, profit or overheads, to detailed operational data such as absenteeism and the control of individual process parameters and product characteristics. This data can either be expressed sequentially as individual values on a continuous scale in yes/no, good/bad, success/failure format, or as summary measures such as mean and range.

‘Cusum’ is a process of subtracting a predetermined value, such as a target, preferred or reference value from each figure in a sequence and progressively cumulating the differences. The graph of the series of cumulative differences is known as a cusum chart. This simple arithmetical process has a remarkable effect on the visual interpretation of the data.

Quality control and performance improvement using qualitative data

BS 5701 Guide to quality control and performance improvement using qualitative (attribute) data will help lift the burden of collecting and reporting data.

The BS 5701 series focuses on the practical non-statistical treatment of the gathering and charting of qualitative data. It is written in a clear and accessible styl, and is suitable for people who are not experts in this field. Users of the standard will then be able to communicate and explain the methods employed across their organization.

Click here for standards and publications available.

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